The scrutiny isn't over for Rice. Mayor Stephanie Rawlings-Blake issued a statement saying the lieutenant will face a departmental administrative review now that the trial is over.

"This has been a very difficult time for our city, and I thank the community for their patience during this time and ask their continued respect for the judicial process as we move forward," she said.

Gene Ryan, president of the Baltimore City Fraternal Order of Police, said he was pleased with the judge's ruling and took the occasion to lambaste State's Attorney Marilyn Mosby and demand she call off the "malicious" prosecutions of the two officers who remain to be tried and the one scheduled to be retried.

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"If Mrs. Mosby's office is willing to violate rules in these high-profile cases, we can only imagine what her office is doing in the cases that affect the citizens of Baltimore every day when the media's not around," he said. "The citizens of Baltimore deserve better from Mrs. Mosby's office."

Judge's explanation

Williams spent about 25 minutes explaining the legal rationale behind his ruling and said it was incumbent upon the court to treat the case impartially.

"It is critical for this court not to base any decision on public opinion or emotion," he said.

In sum, prosecutors failed at several levels to prove its allegations, Williams said.

The prosecution wanted the judge to presume Rice had read a general order mandating that officers seat belt prisoners, Williams said, but failed to prove it. There was also no evidence that Rice was aware that failing to seat belt a prisoner might result in injury or death, the judge said.

And while the prosecution was able to prove that Rice made the decision to shackle Gray, and to transport Gray to the police department's Western District rather than central booking, the state presented no indication as to why.

"There are a number of possibilities the court could entertain, some that are innocent and some that are not. However, the burden of proof rests with the state, and the court's imaginings do not serve as a substitute for evidence," the judge said.

Photos:Baltimore officers in Freddie Gray case

Photos:Baltimore officers in Freddie Gray case

Six Baltimore police officers were charged in the April 2015 death of Freddie Gray, who died of a severe spinal-cord injury while in police custody. But there were no convictions in the case. Three of the officers were acquitted before prosecutors dropped the charges against the remaining three in July 2016. Seen here is Lt. Brian Rice, who was part of the bike patrol that arrested Gray. On July 18, 2016, Rice was found not guilty of involuntary manslaughter, reckless endangerment and misconduct in office in connection with Gray's arrest and death.

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Photos:Baltimore officers in Freddie Gray case

Officer Caesar Goodson drove the van in which Gray was fatally injured. On June 23, Goodson was found not guilty on all charges, including the most serious count of second-degree depraved-heart murder.

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Photos:Baltimore officers in Freddie Gray case

William Porter was the first of the six officers to face a trial. It ended in a mistrial in December, and he had been scheduled to be retried before prosecutors dropped the charges against him. Porter was summoned by the van's driver to check on Gray during stops on the way to a police station. Prosecutors said Porter should have called a medic for Gray sooner than one was eventually called, and they said he also should have ensured that Gray was wearing a seat belt. Porter had been charged with involuntary manslaughter, second-degree assault, reckless endangerment and misconduct in office.

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Photos:Baltimore officers in Freddie Gray case

Edward Nero, one of three bike officers involved in the initial police encounter with Gray, was found not guilty of all charges in May. He was accused of second-degree intentional assault, two counts of misconduct in office and reckless endangerment.

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Photos:Baltimore officers in Freddie Gray case

Garrett Miller was another one of the bike officers involved in Gray's arrest. He placed Gray in a restraining technique known as a "leg lace" before Gray was placed in the van, said Marilyn Mosby, the state's attorney for Baltimore. All charges were dropped against Miller, who had been indicted on charges of second-degree intentional assault, two counts of misconduct in office and reckless endangerment.

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Photos:Baltimore officers in Freddie Gray case

Sgt. Alicia White was present during one of the stops to check on Gray's condition. She and two other officers saw Gray unresponsive on the floor of the van, and when White spoke to Gray and he did not respond, she allegedly did nothing to help him, prosecutors said. All charges were dropped against White, who had been indicted on charges of involuntary manslaughter, second-degree negligent assault, misconduct in office and reckless endangerment.

Protests were thin outside the courthouse. Before the ruling, only a couple of protesters were present. One had a "Justice for Freddie Gray" sign, while the other held up a sign that read, "God never fails."

Same judge acquitted Nero, Goodson

Rice was one of the three officers on bike patrol the morning Gray was arrested, and he was the officer who put Gray into the transport wagon after he was shackled -- failing to fasten his seat belt, according to the testimony of other officers.

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Of the six officers charged, Goodson faced the most serious charges, including second-degree depraved-heart murder. Legal experts have said Goodson's acquittal last month could set the tone for officers still awaiting trial.

"It does not bode well for prosecution," CNN legal analyst Danny Cevallos said.

Williams' verdict in Goodson's case sent "a message to the public and to the courts and the prosecution that if you can't convict beyond a reasonable doubt as to a high charge like murder, what does it say about lesser crimes?"

Final witnesses: Medical experts

The final two defense witnesses in Rice's trial were medical experts who both said it was clear Gray's injuries happened all at once, and they happened while the van was on its way to the final stop.

Dr. Matthew Ammerman, a neurosurgeon, concluded that Gray's neck injury occurred immediately before the van's final stop. At the earlier van stops, Gray was talking, and there were no signs of a broken neck.

Freddie Gray, 25, died seven days after he was fatally injured in April 2015.

The testimony was key to the defense's theory that Gray didn't need help at the van's earlier stops.

The state argued Gray was injured earlier and he got progressively worse during the van ride and needed immediate medical help.

Rice did not take the stand but acknowledged in court he understood he had the option to testify.

Other officers testify

Nero, who was found not guilty, and Officer William Porter, whose trial ended in a hung jury in December, were called to the stand to testify.

Nero testified that Rice put Gray into the transport van after he was shackled. He said Rice pulled him by his arms, left him face down on the floor and then climbed or slid over him to get out.

Responding to questions from the defense, Nero said Gray was flailing and at times resisting.

"The floor was deemed a better position," he said, because more force would have had to be used to get Gray onto a bench.

Porter, who will be retried in September, was forced to testify under immunity granted by the state.

He described Gray's position in the van, recalled his request for help and explained how he "assisted" him to the van's bench.

He asked Gray if he wanted to go to the hospital, and was told "yes," according to Porter's account.

When questioned by the defense, Porter said at that point Gray was speaking to him, making eye contact and did not show any obvious signs of injury.

The defense was not allowed to question Porter about earlier van stops since the state hadn't mentioned them. However, it was allowed to use Porter's prior testimony as evidence -- specifically, comments about the crowd in the area where Gray was arrested, in which Porter described the need for "crowd control."

Goodson, Nero and Officer Garrett Miller were in court for the verdict. Miller is slated to stand trial next.

2 charges dropped

Earlier this month, the judge granted a defense motion to throw out one of the charges against Rice, saying the state failed to show he committed assault.

Prosecutors had argued Gray was assaulted and the instrument of the assault was the police van. However, Williams noted the state didn't prove that Rice ever had control of the vehicle or collaborated with the driver to harm Gray.

Earlier in the trial, the state dropped a charge of misconduct in office against Rice for making an arrest without probable cause after it said he was not directly involved in Gray's arrest.